1. Field of Invention
The present invention relates to a conversion device and, in particular, to a single-stage AC to DC conversion device.
2. Related Art
The power factor is defined as the ratio of the real power to the apparent power, or represents the cosine of the phase angle formed by the voltage waveform and the current waveform. The power factor is between 0 and 1, which means, the load on the circuit is a resistive load, a capacitive load, or an inductive load.
Idealistically, the power factor equals to 1, which means the load on the circuit is purely a resistive load and the voltage waveform representing the load has the same phase with the current waveform. When the power factor is not equal to 1, which means the load on the circuit is a capacitive load or an inductive load, such that a part of the apparent power is converted into the real power and another part of the apparent power is converted into a reactive power. The real power is the power consumption occurred by completing the actual operation of the load, for example, the power consumed to activate a motor. The reactive power is the energy consumption occurred by completing the actual operation of the load.
To reduce the energy consumption occurred by the reactive power, the prior art is to provide an AC to DC conversion circuit. FIG. 1 is a schematic view of a conventional AC to DC conversion circuit 1. With reference to FIG. 1, the conventional AC to DC conversion circuit 1 includes an AC power supply 16, a full-bridge rectifier 11, a first transformer 12, a second transformer 13, and a switch 14. The first transformer 12 is electrically connected to the full-bridge rectifier 11 and the second rectifier 13. The switch 14 is electrically connected to the second transformer 13.
The AC power supply 16 outputs an AC signal S01 to the full-bridge rectifier 11 that outputs a DC signal S02 according to the AC signal S01 and sends the DC signal S02 to the first transformer 12. The first transformer 12 receives the DC signal S02 and the second transformer 13 outputs a DC signal S03 to the load 15 according to the DC signal S02 and the on or off status of the switch 14.
The conventional AC to DC conversion circuit 1 processes the signal conversion through the first transformer 12 and the second transformer 13. However, after operating two transformers, the conversion loss will occur twice.
In addition, the current electronic devices tend to be lighter, thinner, shorter, and smaller in size. The number of elements may be decreased if the first transformer 12 and the second transformer 13 are integrated into one element, such that the electronic device may be smaller or lighter and the conversion loss may be reduced, so as to lower the production cost and enhance the efficiency. Thus, it is an important subject to provide the single-stage AC to DC conversion device that can reduce the number of elements and decrease the conversion loss of the energy.